1. Field of the Invention
The present invention relates to a moving optical system assembly for exposing an image to light that is arranged under a contact glass for supporting a document on the upper surface of a frame of a copying machine.
2. Description of the Prior Art
A method of forming an image using a copying machine usually consists of placing a document on a transparent contact glass, exposing an image to light by irradiating the document with light through a contact glass while being scanned by a source of light such as halogen lamp, focusing the reflected light on a photosensitive material through an optical system such as a mirror or a lens to form an electrostatic latent image corresponding to the document image, developing the electrostatic latent image to form a toner image, and transferring the toner image onto a predetermined paper followed by fixing.
The source of light is secured to a moving frame together with the mirror which introduces the light reflected by the document into the lens, and the moving frame is moved under the lower surface of the contact glass to expose image to the light.
The moving frame is in many cases provided with an arm which contains document sensors for detecting the document size. That is, a document placed on the contact glass is automatically detected for its size, and the paper of a size corresponding to the size of the document is fed based upon the detection signal thereby to form image thereon.
In order to obtain a vivid image by the above-mentioned image formation, the surface of the contact glass on which the document is placed must be kept clean. When the surface of the contact glass is contaminated, exposure of the image to light is impaired and the image being formed is adversely affected.
In the conventional copying machines and particularly those which are equipped with a document sensor arm, there exists a problem in that dust tends to adhere to the lower surface of the contact glass. If it is the upper surface of the contact glass onto which the dust adheres, then, the surface can be easily wiped by a user without arousing any problem. However, if the lower surface of the contact glass is contaminated, it cannot be easily wiped by the user. Because of this reason, therefore, the period of maintenance is shortened arousing a new problem, and improvements have been desired.